Heat pump devices (air conditioners, etc.) generally comprise a four-way reversing valve as a flow path (flow direction) reversing means in addition to a compressor, a vapor-liquid separator, a condenser (outdoor heat exchanger), an evaporator (indoor heat exchanger), an expansion valve, etc. (see JP Patent Publication (Kokai) No. 2001-295951 A (Patent Document 1), etc.).
However, with such heat pump devices employing a four-way reversing valve, since a high-temperature and high-pressure refrigerant and a low-temperature and low-pressure refrigerant flow in close proximity to each other within the four-way reversing valve, there is a problem in that the amount of heat transferred (heat transfer amount) from the high-temperature and high-pressure refrigerant to the low-temperature and low-pressure refrigerant becomes greater, thereby causing non-negligible heat loss and a drop in thermal efficiency.